Set color schemes from external tools

[Yaraslaut]

add support of https://github.com/Gogh-Co/Gogh to configure terminal colors

[christianparpart]

I think, to make it easier for the user to quickly tweak the look, we should also provide some pre-installed colorschemes that are compatible with Contour.

We could get inspired by Gogh. While PR'ing into their repo to make it compatible with Contour would work, I think we should ourself come with a smallish (decent) set of colorscheme variations already.

At least the most well known should be provided. Otherwise, as long as licence permits, we could create a conversion script that helps creating the initial set of pre-installed colorschemes.

Here's a list of my favourite colorschemes from the past:

• Monokai
• Onedark
• Onelight
• Gruvbox
• Solarized
• Base16 (variations)
• PaperColor

The other note is, that Contour supports way more color entries per color scheme than others. We'd need to fill these out manually to provide some good-looking default.

[Yaraslaut]

I added predefined color palettes in the contour, so now users can config it easier, thus i will close this one as complete